SMT's basic requirements for SMT can be summed up in three sentences: first, it should be accurate; second, it should be well pasted; third, it should be fast.
(1) It's accurate
Pasted accurately contains the following two meanings.
① Correct components: it is required that the type, type, nominal value, polarity and other characteristic marks of the equipment in each assembly direction shall meet the requirements of the assembly drawing and detailed list of the product, and the wrong orientation shall not be pasted.
② Accurate orientation: the ends or leads of meta equipment should be aligned and centered as far as possible in orientation and angle with the policy graphics. In addition to the traditional pad graphics on PCB, the current alignment policy is based on the solder paste graphics printed in practice.
(2) Good job
A good post contains the following three meanings.
① No damage to components: when picking and mounting, the errors of feeder, meta equipment, PCB and z-axis control may cause damage to the components, resulting in mounting failure.
② Proper pressure (chip height): the pressure (height) of the chip should be appropriate. If the pressure of the chip is too small, the solder end or pin of the meta equipment will float on the surface of the solder paste, and the solder paste will not stick to the meta equipment, and it will simply move in the direction during transmission and reflow soldering; if the pressure is too high, the solder paste will be easily adhered; if the pressure is too high, it will even damage the meta equipment.
③ Ensure the placement rate: the improper adjustment of the placement machine parameters, the poor mounting function of the meta equipment, and the defects of the feeder and suction nozzle will lead to the drop of the meta equipment during the mounting process. This phenomenon is called "chip dropping" or "throwing". In practical production, with the "mounting rate" to measure, when the mounting rate is lower than the booking level, we must check the reasons.
(3) Stick it fast
Generally, there are tens to thousands of components on a circuit board. These components are pasted one by one. The mounting speed is the basic requirement for the production power (capacity). The speed of mounting mainly depends on the speed of the placement machine, and is closely related to the optimization of the mounting process, the use and management of the equipment